Out of the questions solved by a student the number of incorrect solutions was twice the correct answers. He solved 48 questions. How many answers were correctly solved?

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RRB TC CC Exam (Bangalore) 2006 click here to view all questions

Out of the questions solved by a student the number of incorrect solutions was twice the correct answers. He solved 48 questions. How many answers were correctly solved?

A12

B16

C24

D18

Sachin Khr ? Nov 18 '2016 at 22:38

Answer is: 16
Let he has solved correctly X no. of sums. Therefore incorrect no. of sums = 2X .
Now,
X +2X = 48
3X = 48
X = 16 sums he has done correctly.

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RRB TC CC Exam (Patna) 2006 click here to view all questions

Simplify: to get

A18

B22

C20

D24

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A two digit number is five times the sum of its digits. If 9

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RRB TC CC Exam (Bangalore) 2007 click here to view all questions

A two digit number is five times the sum of its digits. If 9 is added to the number, the digits interchange. Find the sum of the digits.

A11

B7

C6

D9

quiaz ? Dec 20 '2018 at 14:16

Let a and b the digits we can write the number as "ab" but the number is \(10 \times a+b\)
(for example if a=3 and b=2 the number would be 32 and \(32 =10 \times 3+2\)) 

a two digit number is 5 times the sum of its digit then \(10 \times a+b=5(a+b)\)
when 9 is added to the number the result is the original number with its reversed \(10 \times a+b+9=10 \times b+a \)
then we have the following equations: 
\(10 \times a+b=5(a+b)\)
\(10 \times a+b+9=10 \times b+a \)
then 
\(10a+b=5a+5b\)
\(10a+b+9=10b+a \)
then 
\(5a-4b=0\)

 
\(9a-9b=-9 \)
then 
\(5a-4b=0\)
\(a-b=-1\)
then using 2nd eq a=b-1 
using 1st eq \(5(b-1)-4b=0 \)
then \(5b-5-4b=0\)
then b=5 and a=5-1=4 
the sum of digits is 9.

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A 2-digit number is 3 times the sum of its digits. If 45 is

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RRB ASM Exam (Ajmer) 2007 click here to view all questions

A 2-digit number is 3 times the sum of its digits. If 45 is added to the number, its digits are interchanged. The sum of digits of the number is-

A11

B9

C7

D5

Nithin K ? Nov 20 '2016 at 19:27

Answer is : 9

Explanation:

A 2-digit number is 3 times the sum of its digits.
10y + x = 3(x + y)
10y + x = 3x + 3y
2x - 7y = 0 .........................(i)

If 45 is added to the number, its digits are interchanged.
10y + x + 45 = 10x + y
9x - 9y = 45 .......................(ii)

On Solving equation (i) and (ii)
x= 7
y= 2
number = 27
sum of the digits =(x+y)=(7+2)= 9

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is equal to

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RRB TA Exam (Chennai) 2008 click here to view all questions

A1

B1.5

C2

D2.5

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